The present invention relates generally to the field of snow skiing and in particular to a new and useful ski construction having increased traction and control in packed and icy snow.
The basic flat design of ski running surfaces dates back more than one hundred years and is quite adequate for its initial intended purpose of floating on, or pushing against, powder snow and soft packed snow. As skiing evolved into a competitive and recreational sport, the typical ski terrain shifted from powder and soft-pack to predominantly groomed hard packed snow and sometimes ice. In order to deal with these conditions, virtually all modern skis have hardened steel edges running from front to back along both left and right sides of the bottom surface. These edges are machine ground along with the plastic bottom of the ski to form one smooth continuous surface.
Steel edges may be superfluous in loose powder conditions but when hard-pack snow and ice are encountered, the skier must angle the ski such that one of the two steel edges will “bite” into the hard surface. Otherwise, the skier cannot create a controlling force through the friction of a skid. Similarly, snow-glider type skiers and hyper-carving skiers must create even more extreme positive engagement with the snow surface so that the edge properly “tracks” through the hard surface without skidding. The blade geometry or configuration of an ice skate is most effective for digging into a surface. In contrast, the configuration of a conventional ski is extremely counterproductive to this important function.
FIGS. 1–4B are provided to illustrate the principles on which the invention herein is based.
FIG. 1 illustrates a rear view of an ice skate 2 going straight on the surface 5. Arrow F indicates that the force exerted by the skater (primarily in the form of gravity, or weight) is directed completely aligned with the skate blade 1, perpendicular to the skating surface 5. The pressure exerted on the ice is extremely high, mainly because the blade 1 is narrow and presents very little surface area to the ice 5, thereby forcing the blade 1 to bit into the ice 5.
As the skater begins to bank into a left turn, the blade 1 naturally angles to the left, as illustrated by FIG. 2. The skater's force F is now directed at an oblique angle θ to the skating surface 5, and has two components—a horizontal (centrifugal) force CF and a downward force W. The resulting centrifugal force CF is directed to the right, but the sharp edge of the blade 1 is angled in a manner to “dig into” the ice of the skating surface 5, thus preventing any unwanted skidding. The ice provides an equal force against the force F produced by the skater. Newton's Law thereby requires the skater to turn to the left, rather than skid to the right.
It is important to differentiate this positive dig angle from a negative slide or skid angle. When an acute angle θ exists between the blade 1 and the surface 5 in the intended direction of movement (the force is directed opposite to the movement), a dig angle is achieved. If the blade 1 is at an acute angle to the surface 5 to the side opposite the intended direction of movement, a skid angle is produced. For example, consider sliding the skate blade 1 of FIG. 2 across the surface toward the left; clearly the blade 1 will easily move to the left as it slides across the surface 5. In contrast, trying to push the skate blade 1 to the right while at the same angle will be very frustrating, as it digs into the ice, preventing movement to the right.
Thus, an ice skating blade 1 is normally always operating in a dig angle mode, and never at a skid angle, because the skater's force is always directed from the side of the blade 1 forming the acute angle with the surface 5. Moreover, as the turn gets tighter and/or faster, the angle θ decreases proportionately, as does the dig angle of the blade. Thus the ice skating blade naturally assumes a proportionately appropriate dig angle to the ice surface in order to always cope successfully with the outward centrifugal force. This is why an ice skater rarely skids out during a turn.
The same analysis of a ski turn reveals the problem that plagues all skiers attempting to turn on a hard packed or icy surface 5.
FIG. 3 illustrates a ski 4 going straight on a typical groomed hard packed surface 5. As with the skater, all of the skier's force F is directed downward at the skiing surface 5, but through the flat running surface 4a of the ski, rather than a blade. Unlike a skate, the running surface 4a of the ski presents a large contact surface area to the skiing surface 5. This dissipates the total force F, so that the pressure exerted against the skiing surface (such as measured in p.s.i.) at any portion is significantly less, relative to the force exerted by the skater. The skier is effectively in an ultimate skid or slide condition as the angle between the edges 3a and 3b and surface 5 is zero.
FIG. 4A illustrates the right ski 4 of a skier making a left turn by lifting the right 3b edge and placing more weight on the left edge 3a. As should be clear, the skier remains in a skid angle α with the snow surface 5 instead of forming a dig angle θ. This is so because ski running surface 4a is roughly equivalent to the side of skate blade 1 in this analysis, and the acute angle α is formed in the side opposite the intended movement. Centrifugal force CF will easily overcome friction between the edge 3a and surface 5, causing a skid, rather than dig. This is especially true when the ski 4 forms the usual low skid angle α occurring during a ski turn. It is nearly impossible for a conventional skier to positively engage the snow surface 5 in a dig angle because the ski 4 and ski edges 3a, 3b simply do not permit creation of a dig angle during a turn.
This is why the majority of recreational skiers never come close to achieving the positively engaged carved turn of the ice skater; every attempt to edge the ski results in an extreme skid angle and the inevitable skid. Thus virtually all recreational skiers are skid skiers who attempt to use the friction of the skid to control speed and direction. Some control is possible at all due to skid friction generated between the edge 3a and ski running surface 4a with the snow surface 5.
FIGS. 1–4B should also make clear why a recreational skier finds carving so difficult when it is understood how an expert skier or ski racer achieves this feat. After significant training and with great strength, the expert skier takes a giant leap of faith past the extreme skid angle and angulates the ankles, knees, hips, and pelvis to place the active ski edge 3a almost vertical to the snow surface 5. This angulation is illustrated in FIG. 4B.
It is important to realize that even with the most extreme angulation, the expert skier can never achieve a positive engagement dig angle but only reduce the skid angle to a minimum. Since even the expert skier can never achieve a dig angle it is imperative to maximize the grip of this compromised edge angle with additional down force. This is done in a manner similar to Indy-style racecars that use wings to create additional down force on the tires, which results in greater grip and cornering ability.
The contortions of extreme angulation are mandated not only to get the ski almost vertical in order to minimize the skid angle, but also to create this additional down force on the edge that prevents skidding out. The extreme bending of the torso at the waist, combined with the legs in a position almost parallel with the snow surface, creates a clockwise torque that is balanced by greater downward force on the ski edges. The entire weight of the skier's body, plus the centrifugal force and torque of the turn, must be supported by the lateral abductors and adductors of the leg muscles as well as the oblique and abdominal muscle structure of the torso/hips while in this angulated contortion. These are muscle groups that are rarely, if ever, used by the average person or recreational skier. It is ludicrous to expect anyone other than a highly trained athlete to achieve this great feat of strength and agility.
In contrast, the ice skater is not required to master these strenuous feats of contortion because the skate blade is always at a dig angle and does not require additional angulation or down force to prevent skidding. The simple and casual turn position of a skater permits the skater to keep their body in a natural standing position parallel to the forces during turning. There are no contortions or need for inordinate strength from any muscles. The skater merely leans into the turn and stands up in a normal fashion against the turning forces.
Some skis and snowboards have been proposed having different running surface configurations for a variety of reasons.
U.S. Pat. No. 4,083,577 describes a ski having a convex running surface and blade edges extending along the sides of the ski adjacent the boot bindings. The blade edges extend to about the depth of the convex surface apex. The blades are provided to enhance the turning and gripping and resemble ice skate blades, but are formed with a single edge. The running surface lacks a flat area.
U.S. Pat. No. 3,304,095 teaches a very specific configuration for a pair of skis. The skis have a transversely sloped running surface from the inner edges toward the outer edges. The running surface of each ski is inclined upwardly from the inner edge toward the outer edge. The running surface slopes sharply downward near the outer edge, from which point a second upwardly inclined surface joins the outer edge. The particular running surface configuration provides a triangular channel in the running surface of each ski, the greatest depth of which is adjacent the outer edge of the ski.
U.S. Pat. No. 5,462,304 discloses a snowboard having interchangeable, dual-acting edges which extend continuously along the outside length of the active board edge. The interchangeable edges are provided to make repair and maintenance easier, as well as providing a simple method for adapting the snowboard to the skiing surface conditions. The interchangeable dual-acting edges each have a pair of control edges, one elevated above the other. The lower, first edge is oriented facing inwardly toward the board center, while the upper, second edge faces outwardly. The first edge contacts the skiing surface during level, flat riding, while the board be rolled onto the second, elevated edge in a sharp turn. The second edges act similar to a governor and provide stability in sharp turns so that the snowboarder can return to the first, lower edges without falling. The orientation of the edges is arranged to prevent the second edges from creating instability when the board is flat.
A snowboard with a longitudinal tunnel along the length of the running surface is taught by U.S. Pat. No. 6,224,085. Several orthogonal protrusions are mounted inside the tunnel for contacting the snow surface. Flat sides with conventional outer edges are provided on each side of the tunnel. In use, the protrusions are intended to contact snow passing through the tunnel to provide better turning control than the conventional outer edges alone.
U.S. Pat. No. 3,503,621 illustrates a fiber glass composite ski having a small groove along the center of the running surface near the front end of the ski. The ski body is wider on either side of the groove that the width of the groove. The purpose of the groove is not revealed in the patent.
U.S. Pat. Nos. 5,040,818 and 5,145,201 both teach a snow mobile ski runner having a center running blade and elongated cylindrical wear bar mounted to the bottom middle of a center concave portion and a pair of horizontally extending concave surfaces vertically offset above the center concave portion. The horizontally extending concave surfaces are provided as primary steering surfaces and extend along the length of the ski on each side. The center wear bar is provided for when the ski is running on icy surfaces.
The inventor herein has proposed a new type of ski called a snow glider for producing positive engagement with the snow using an extremely narrow ski. The snow glider is described in co-pending application Ser. No. 10/286,643 filed Oct. 31, 2002. Generally, the snow glider relies upon a narrow waist section in a primary ski having a conventional shape running surface alone or in combination with a secondary edge mounted above the primary ski to provide enhanced turning.
Clearly, skiing could be made easier, especially for casual recreational skiers, if a ski were available which has edges that produce positive engagement, or dig angles, during turns as opposed to skid angles.